In the last decade the Wi-Fi has become the networking technology of choice at home and at enterprises for wireless users. It is also abundantly present at locations of nomadic computing such as cafes, airports and hotels. The umbrella wireless coverage is usually from macro-cellular network but the cost of carrying wireless data is significantly higher on macro-cellular network.
Many modern devices used by mobile user base (e.g., Smartphone, tablet, and laptop) are capable of using both Wi-Fi and cellular network. So it would seem logical to provide a seamless connectivity service that uses these complementary networks efficiently. Under the umbrella of fixed mobile convergence, there have been many efforts by the industry and by standards bodies to address this need. The interworked WLAN (IWLAN) is one such effort that is standardized by the third generation partnership project (3GPP). Even though IWLAN is an end to end solution complete with standardized architecture and protocols, it has basic shortcomings on the end user device implementation and the user experience aspects. That has limited its usefulness in practical deployment.
As the packet data traffic on a macro-cellular network continues to rise and ruggedized Wi-Fi access points have become available for outdoor use, with these developments, the urgency and the ability of Wi-Fi to complement macro-cellular has increased considerably. Moreover, mobile operators can simply use a service set identifier (SSID) on a campus wide Wi-Fi deployment. Large Wi-Fi deployments have moved away from ad-doc stringing of cheap access points to more sophisticated, high performance and distributed Wi-Fi systems and centralized controller with sophisticated algorithms for power and interference management.
Whenever a wireless node attaches to a network, it must get authenticated, authorized and the network must remain aware of its point of attachment. In simple terms a wireless session needs to be established from the mobile device to the network. Depending on the coverage area of the service, the network must keep track of user's point of attachment (mobility management). It must also provide a topologically correct IP path to the mobile node for the user data flows. When Wi-Fi and macro-cellular 3G network operate in a disjointed manner, not only these function are executed in duplicative manner, user does not get benefit of seamlessness either.